The present invention relates to a film-forming agent which forms film on the skin, and also to a transdermal preparation containing the film-forming agent and active ingredient.
Recently, various transdermal preparations have been developed for the purpose of delivering active ingredient such as drug through the skin, or supplying active ingredient to the skin itself.
Such formulation can be divided into xe2x80x98formulation of being appliedxe2x80x99 and xe2x80x98formulation of being spreadxe2x80x99, and the former includes adhesive preparation such as plaster and cataplasm, and the latter includes spreadable semi-solid preparation such as cream, ointment and gel.
The externally applying preparation has advantage of capability of delivering active ingredient at the attached site for a desired amount of time while exhibiting defects of appearance problem upon applying to exposed part, inconvenience, difficulty to apply to curved region of body, skin irritation by repeated use to same site. Additionally, necessity of using extra supporting material (cotton, film, release paper etc.) raises cost.
On the other hand, the said spreadable semi-solid preparation can be applied regardless of shape or area of the application region, and freely applied even to exposed region. In addition, even when used repeatedly on the same site, skin irritation is lower than the adhesive preparation. However, the preparation such as ointment or cream is sticky and soils clothes or socks, and should be applied several times a day due to being easily smeared out.
Therefore, there has been demand for a film-forming agent that can overcome the defects of the said two formulations.
In general, as polymer which can form film upon application to the skin, poly(vinyl alcohol), cellulose, carboxyvinyl polymer, poly(vinyl pyrrolidone) etc. can be used.
As an example of drug delivery system using such film-forming polymer, U.S. Pat. No. 4,393,076 discloses gel preparation formulation for antiphlogistic analgesia using cellulose, carboxyvinyl polymer as film-forming agent, and Korean Patent Publication 96-8225 reports percutaneous formulation such as antiphlogistic analgesic, nicotine using as fast film-forming agent such as poly(vinyl alcohol), poly(vinyl pyrrolidone), cellulose or pectin etc., Korean Patent Laid-open Number 98-076273 reports transdermal film-forming gel formulation using poly(ethylene oxide), methoxyethylene maleic anhydride copolymer, cellulose derivatives, vinyl acetate-vinyl pyrrolidone copolymer and poly(vinyl alcohol), Korean Patent Laid-open Number 98-072361 discloses soft hydrogel external preparation comprising poly(vinyl pyrrolidone-xcex1-acrylic acid) and poly(vinyl alcohol), and Korean Patent Publication No. 97-5282 discloses gel preparation using poloxamer containing propionic acid-series non-steroidal antiphlogistic analgesic drug.
However, the film-forming polymers used in the said references are defective in that they interfere with body movement due to lack of elasticity, high glass transition temperature brings collapse of the film formed after drying, leading to easy exfoliation from the skin.
Therefore, the present invention intended to develop a film-forming agent to which polyurethane is introduced, which is flexible due to low glass transition temperature, and allows free body movement for high elasticity.
On the other hand, as previous studies on such polyurethane, inventions for implant material such as catheter, heart valve based on high biocompatibility of polyurethane can be referred to. For example, U.S. Pat. No. 5,041,100 disclosed a study on reduction of friction occurring at the time of catheter insertion by modifying the surface of catheter with polyurethane, and U.S. Pat. No. 5,017,664 discloses a study for raising blood compatibility of medical instrument by developing biocompatible polyurethane.
Also, studies to develop polyurethane as substrate for external preparation were carried out. For example, Published International Patent Application WO 99/14283 suggested to deliver active ingredient with pressure-sensitive adhesive containing polyurethane, acrylic acid alkyl ester and vinyl acetate-type polymer, fatty acid or polyols, and Publishes International Patent Application WO 90/00066 presents polyurethane drug delivery system requiring second substrate, e.g. a method of spreading polyurethane containing external antibacterial agent on the skin by being dissolved in solvent, then by being covered with polyurethane film.
Additionally, as an invention for forming drug-delivering film on the skin by being spread in a state of solvent without the second substrate, U.S. Pat. No. 4,560,555 intended to develop polyurethane film substrate reacting directly to damaged skin as external protector for drug delivery, but this exhibited defect, safety problem for chemical reaction with the skin, difficulty to freely detach the attached film at any desired time point due to chemical binding.
On the other hand, in case of polyurethane film-forming agent, which is spread in a state of solvent while exhibiting no reaction with the skin, it is defective for being easily detached from the skin due to insufficient adhesion of polyurethane.
Therefore, to make up for such disadvantage, studies for introducing into polyurethane a second polymer having functional group capable of making secondary bonding with skin were conducted. For example, U.S. Pat. No. 4,542,012 relates to study on film-forming formulation containing antibacterial agent and introduced poly(vinyl pyrrolidone) in the synthesis of polyurethane. However, to introduce poly(vinyl pyrrolidone) during the polyurethane synthesis, an additional synthetic process for introducing isocyanate functional moiety into poly(vinyl pyrrolidone) is necessary. Yet, such a synthetic process is complicated and has difficulty in molecular structure control. Further, polyurethane synthesized by such process does not easily form microphase separation structure, so desired elasticity and flexibility is difficult to obtain, and polyurethane with desired molecular weight is difficult to obtain for steric hindrance due to side chain functional group. Also, it has no advantage in adhesion property, thus is difficult to apply to body of repeated movement.
As another method for supplementing the insufficient adhesion of polyurethane, there is a method of physical blending with the second polymer with functional group capable of making secondary chemical bonding with the skin. Yet, in this method, it is important to avoid phase separation by compatibility between polyurethane and the second polymer. Korean Patent Application No. 2000-18566 synthesized polyether as the second polymer with functional moiety to make secondary chemical bonding with the skin, phase separation was prevented by being synthesized to have identical main chain with polyurethane.
However, in this case, when main chain of polyurethane is changed, inconvenience occurs, that is, main chain of polyether should be also modified.
On the other hand, although U.S. Pat. Nos. 5,156,601 and 5,258,421 performed studies on a preparation for forming stable film on the skin through proceeding studies on sticky dressing gel comprising polyurethane and poly(N-vinyl lactam) dispersed in aqueous solution, this preparation also failed to exhibit advantage in flexibility and elasticity.
Therefore, the inventors of the present invention intended to develop a film-forming agent with superior elasticity, flexibility and adhesion power and transdermal preparation containing the same, through solving the problems of the previous inventions.
As the result, as the film-forming agent that can completely satisfy the said physical and chemical feature, the present invention developed xe2x80x98blendxe2x80x99 of (A) thermoplastic polyurethane and (B) addition polymerization polymer having a functional group of carboxylic acid derivative at main chain or side chain.